Apparatus and method to control and calibrate deliberate speed mismatch in color IOTs

Abstract

A method and apparatus for controlling speed match between a photoreceptor and an intermediate transfer member to prevent image degradation by creating a deliberate speed mismatch. It has been found that slight variations in speed match between a photoreceptor and transfer member will maintain acceptable image quality, however, should the relative velocity between the members change sign, unacceptable image error results. The method herein comprises slewing the velocity of a photoreceptive member over a range of speeds while monitoring the output control signal current of a drive motor. The resulting control signal current has a large oscillation at the velocity at which the speed of the photoreceptor matches that of the intermediate transfer member. A controller is then used to maintain the motor velocity at a speed slightly less than or slightly greater than the intermediate transfer member speed so as to prevent a change in sign of the relative velocity between the two moving surfaces.

We claim: 
     
       1. A method of controlling the relative velocity between an image bearing member and an image receiving member of a printing machine, comprising: determining the relative velocity between the image bearing member and the image receiving member; and   adjusting the relative speed of the image bearing member and the image receiving member so that there is a velocity mismatch within a preselected range, therebetween.   
     
     
       2. A method according to claim 1, wherein said determining step comprises: slewing the velocity of the image bearing member over a variable range of allowable drive speeds; and   monitoring the current of a motor driving the image bearing member while performing the velocity slewing step.   
     
     
       3. A method according to claim 1, wherein said determining step comprises: slewing the velocity of the image receiving member over a variable range of allowable drive speeds; and   monitoring the current of a motor driving the image receiving member while performing the velocity slewing step.   
     
     
       4. A method according to claim 1, further comprising detecting the amplitude of a motor current signal which corresponds to a velocity match between the image bearing member and the image receiving member and maintaining a mismatch in velocities. 
     
     
       5. A method according to claim 1, wherein said adjusting step comprises setting the velocity mismatch to a preselected range of speeds, wherein said preselected range is selected to maintain an unchanged polarity between the image bearing member and the image receiving member. 
     
     
       6. A method according to claim 5, wherein said adjusting step comprises setting a motor velocity so that the image bearing member operates in a range at a speed slightly greater than but not equal to that of the image receiving member. 
     
     
       7. A method according to claim 6, wherein adjusting step comprises adjusting the relative velocity between the image receiving member and the image bearing member so that the velocity of the image bearing member is about 0.167% greater than the speed of the image receiving member. 
     
     
       8. A method according to claim 5, wherein said adjusting step comprises setting a motor velocity so that the image bearing member operates in a range at a speed slightly less than but not equal to that of the image receiving member. 
     
     
       9. A method according to claim 8, wherein wherein adjusting step comprises adjusting the relative velocity between the image receiving member and the image bearing member so that the velocity of the image bearing member is about 0.167% less than the speed of the image receiving member. 
     
     
       10. A method for maintaining the proper relative velocity between a photoreceptor and an intermediate receiving member in an electrophotographic printing machine, comprising: determining the relative velocity between the photoreceptor and the intermediate receiving member; and   adjusting the speed of the photoreceptor so that there is a slight velocity mismatch between the photoreceptor and the intermediate receiving member.   
     
     
       11. A method according to claim 10, wherein said determining step comprises: slewing the drive speed of the photoreceptor within a preselected range approximately equal to the velocity of the intermediate receiving member;   monitoring the output current of a motor driving the photoreceptor while the speed slewing step is performed; and   setting the drive speed of the photoreceptor to a speed not equal to that of the intermediate receiving member.   
     
     
       12. A method according to claim 11, further comprising detecting the amplitude of the motor current signal which corresponds to the velocity match between the photoreceptor and the intermediate receiving member and maintaining the velocity of the photoreceptor at a speed not equal to the detected equal velocity. 
     
     
       13. A method according to claim 11, wherein said setting step comprises varying the motor velocity so that the photoreceptor moves at a speed slightly greater than but not equal to the intermediate receiving member. 
     
     
       14. A method according to claim 13, wherein said setting step comprises adjusting the relative velocity between the intermediate receiving member and the photoreceptor so that the velocity of the photoreceptor is about 0.167% greater than the speed of the intermediate receiving member. 
     
     
       15. A method according to claim 11, wherein said setting step comprises varying the motor velocity so that the photoreceptor moves at a speed slightly less than but not equal to the intermediate member. 
     
     
       16. A method according to claim 15, wherein said setting step comprises adjusting the relative velocity between the intermediate receiving member and the photoreceptor so that the velocity of the photoreceptor is about 0.167% less than the speed of the intermediate receiving member. 
     
     
       17. A printing machine having an image bearing member and a moving image receiving member, comprising: a motor for moving the image bearing member;   a controller associated with said motor, for regulating said motor to move the image bearing member at a velocity either slightly greater than or slightly less than a velocity at which the image receiving member moves to maintain a velocity differential between the image bearing member and the moving image receiving member.   
     
     
       18. A printing machine having an image bearing member and a moving image receiving member, comprising: a motor for moving the image bearing member;   a controller associated with said motor, for regulating said motor to move the image bearing member at a velocity either slightly greater than or slightly less than a velocity at which the image receiving member moves, wherein said controller slews the speed of said motor; and   a sensor to monitor a current of said motor while the speed is slewed and to generate a signal indicative thereof, wherein said controller is responsive to the signal generated by said sensor for generating a control signal to set the drive speed of said motor to a speed so that the speed of the image bearing member is not equal to that of the image receiving member.   
     
     
       19. A printing machine according to claim 18 wherein said image bearing member comprises a photoreceptive member. 
     
     
       20. A printing machine according to claim 18 wherein said image receiving member comprises an intermediate transfer member. 
     
     
       21. A printing machine according to claim 18 wherein said image receiving member comprises a copy sheet.